System design interviews assess your ability to design large-scale systems. Even if you're not interviewing at FAANG companies, these skills are increasingly important.
What Interviewers Look For
- Ability to break down complex problems
- Understanding of trade-offs in design decisions
- Knowledge of scalability patterns
- Communication and collaboration skills
The System Design Framework
1. Clarify Requirements (5 minutes)
- Functional requirements: What should the system do?
- Non-functional requirements: Scale, latency, availability
- Constraints: Budget, timeline, existing systems
2. Estimate Scale (5 minutes)
- Number of users (DAU/MAU)
- Data size and growth rate
- Read/write ratio
- Peak vs. average load
3. High-Level Design (10 minutes)
- Draw main components and data flow
- Identify APIs between components
- Choose database types (SQL vs. NoSQL)
- Consider caching and CDN placement
4. Deep Dive (15 minutes)
- Pick 1-2 components to detail
- Discuss data models and schemas
- Address bottlenecks and solutions
- Consider edge cases and failure scenarios
5. Wrap Up (5 minutes)
- Summarize the design
- Discuss trade-offs you made
- Mention future improvements
Key Concepts to Know
- Load balancing and horizontal scaling
- Database sharding and replication
- Caching strategies (Redis, Memcached)
- Message queues and async processing
- CAP theorem and eventual consistency
- Microservices vs. monolith
Practice Problems
- Design a URL shortener (like bit.ly)
- Design Twitter's news feed
- Design a ride-sharing service (like Uber)
- Design a video streaming platform (like YouTube)
- Design a chat application (like Slack)